This invention relates to electro-optic devices such as spatial light modulators, integrated infrared detectors, and optoelectronic integrated circuits generally, and particularly to the fabrication of PLZT-on-sapphire electro-optic components for such devices, permitting integration of the electro-optic devices with semiconductor devices having the same substrate, such as silicon-on-sapphire circuits.
Numerous reports have been published regarding the deposition of PLT and PLZT film on C-plane (1010) sapphire substrates and other substrates by r-f magnetron sputtering. One report is the article entitled "Two-Dimensional Silicon/PLZT Spatial Light Modulators: Design Considerations and Technology," by S. H. Lee et al., OPTICAL ENGINEERING, Vol. 25 (No. 2), page 250 (Feb. 1986). Other reports include: "PLZT Thin Film Waveguides," by T. Kawaguchi et al., APPLIED OPTICS 23(13), 2187 (July 1984); "High Speed PLZT Optical Switches," by O. Yamazaki et al., TECHNICAL DIGEST ON INTEGRATED AND GUIDED WAVE OPTICS, Paper TuA6, OSA (1984); "Ferroelectric (Pb,La)(Zr,Ti)O.sub.3 Epitaxial Thin Films on Sapphire Grown By R-F Planar Magnetron Sputtering," by H. Adachi et al., JOURNAL OF APPLIED PHYSICS 60(2), (Jul. 15, 1986); "Dielectric Properties of PLZT Epitaxial Thin Films," by H. Adachi et al., Proceedings Of The 4th Meeting on Ferroelectric Materials And Their Applications, Kyoto, 1983, JAPANESE JOURNAL OF APPLIED PHYSICS VOL. 22 (1983), Supplement 22-2,pp. 11-13; "Electric-Optic Effects Of (Pb,La)(Zr,Ti)O.sub.3 Thin Films Prepared By R-F Planar Magnetron Sputtering," by H. Adachi et al., APPLIED PHYSICS LETTERS, 42 (10), (May 15, 1983); "Preparation and Properties of Ferroelectric PLZT Thin Films by R-F Sputtering," by M. Ishida et al., JOURNAL OF APPLIED PHYSICS 48,951 (1977); "Epitaxial Growth of Ferroelectric PLZT Thin Films and Their Optical Properties," by M. Okuyama et al., APPLIED PHYSICS 21,339 (1980).
For proper operation of electro-optic devices like those mentioned above, the PLZT film should be transparent and ferroelectric (i.e., attain a perovskite phase and exhibit a strong electro-optic effect).
PLZT exists in two structural forms: perovskite phase and a metastable pyrochloric phase. The perovskite phase (represented by ABO.sub.3) is ferroelectric, whereas the pyrochloric phase (represented by A.sub.2 B.sub.2 O.sub.7) is paraelectric. Within the family of PLZT compositions, the perovskite PLZT (9/65/35) is known to exhibit the largest quadratic electro-optic effect.
The inclusion of Zirconate (Zr) in the composition tends to reduce the transparency of the film. Also, the deposition of the film on a substrate at a temperature below 550.degree. C. tends to reduce the electro-optic effect. When the film is deposited at an elevated temperature (e.g., above 550.degree. C.) on the substrate, and the substrate is maintained at the elevated temperature, the film tends to exhibit the required transparency.
When the temperature of the substrate is raised to above 550.degree. C., however, this satisfies the transparency requirement but causes diffusion of lead outward from the film, leading to lead deficiency in the deposited film, unwanted adulteration of the substrate, and reduced electro-optic effect.
What is needed and would be useful, therefore, is a system and method that could produce electro-optic components with transparent, ferroelectric film characteristics, without lead diffusion.